我正在尝试使用LIFO主体创建一个堆栈。我只需使用推送和弹出功能即可做到这一点。但是我想创建一个迭代器和下一个函数来遍历堆栈。以下是我尝试过的,但无法真正弄清楚逻辑。
class Stack:
def __init__(self):
self.stack = []
self.START = None
self.END = None
def push(self, item):
self.stack.append(item)
#print("item added to stack")
def pop(self):
return self.stack.pop()
#print("value removed according to LIFO")
def emptystack(self):
return len(self.stack) == 0
def __iter__(self):
self.Iterator = self.START
return self
def __next__(self):
if self.Iterator != None:
stack = self.Iterator
self.Iterator = self.Iterator.NEXT
return node
else:
raise StopIteration
def fullstack(self):
return self.stack
s = Stack()
s.push('1')
s.push('2')
s.push('6')
s.push('8')
s.push('11')
s.push('12')
s.pop()
s.push('50')
if s.emptystack():
print("Stack is empty")
else:
print(s.fullstack())
您的 Iterator
属性将始终None
,因为一旦第一次调用下一个,您就会停止迭代。将 next 视为为每个项目调用,直到没有更多项目要处理,来自 Python 文档中关于__next__
:
从容器中返回下一项。如果没有其他项,请引发停止迭代异常
您可以做的一件事是将self.Iterator
初始化为堆栈的长度(以__iter__
为单位),然后在每一步中递减它,直到达到 0(然后提高 StopIteration):
def __iter__(self):
self.Iterator = len(self.stack) - 1 # initialize to the index of the last element
return self
def __next__(self):
if self.Iterator >= 0:
current_value = self.stack[self.Iterator]
self.Iterator = self.Iterator - 1 # update for the next step
return current_value
else: # stop if self.Iterator is -1
raise StopIteration
由于存储堆栈元素list
,因此可以使用 python 的iter
函数返回迭代器并使用它。
class Stack:
def __init__(self):
self.stack = []
def push(self, item):
self.stack.append(item)
#print("item added to stack")
def pop(self):
return self.stack.pop()
#print("value removed according to LIFO")
def emptystack(self):
return len(self.stack) == 0
def stack_iter(self):
return iter(self.stack)
def stack_iter_next(self, iterator):
return next(self.Iterator)
def fullstack(self):
return self.stack
s = Stack()
s.push('1')
s.push('2')
s.push('6')
s.push('8')
s.push('11')
s.push('12')
s.pop()
s.push('50')
s_iter = s.stack_iter()
for x in s_iter:
print (x)